Mid-Heian-period Japanese Tendai 天台 monk and lexicographer at the Mount Hiei Enryaku-ji 比叡山 延曆寺. Japanese name Chūzan 中算 (also read Chūsan); conventional dates 935–976 (Tengyō 8 – Ten’en 4). He was a disciple in the line of Ryōgen 良源 (912–985), the eighteenth Tendai zasu and the principal organising figure of mid-Heian Tendai scholasticism; some Japanese sources also place him in association with Senkan 千觀 of the Tendai exoteric tradition.
His principal surviving work is KR6d0035 Myōhōrengekyō shakumon 妙法蓮華經釋文 (T2189), a three-fascicle lexical-glossary commentary on Kumārajīva’s Lotus Sūtra preserved in the Taishō at T56n2189. The work is a Japanese-context reference manual for the difficult vocabulary, transliterated Sanskrit terms, and obscure proper names of the Lotus, drawing on the standard Tang-period Buddhist lexicographical tools (notably Huìlín’s 慧琳 Yīqièjīng yīnyì 一切經音義 and Xuányìng’s 玄應 earlier Yīnyì) but adapted for the Japanese reading-context. It is the principal pre-modern Japanese Buddhist lexicographical work on the Lotus and was widely copied in medieval Japanese Tendai monastic circles.
Source: hobotei.xml entry TP102; Bussho kaisetsu daijiten 佛書解説大辭典 (Mochizuki); standard Japanese Heian Tendai biographical sources.